Catalytic Converter with Header?!?
 

This is the Exhaust system I'm getting. It installs after the stock Catalytic Converter.
MagnaFlow® 15712 - Honda Civic 2001 Street Series Stainless Steel Cat-Back Exhaust System - Single Rear Exit (Moderate Sound)

Now my question is, is it best to upgrade the Converter and header also when doing the whole Exhaust system? This is the set I was thinking about: MagnaFlow® - Honda Civic 2001-2005 Direct Fit Catalytic Converter with Header

Another question is, if I DON'T upgrade the Converter and header, will my car be okay pushing more air through?

I appreciate the help fellow Civic owners.

You'll be fine to upgrade the cat-back portion without the header/cat. The system you're looking at is very similar to the Magnaflow setup I had, which bolted up to the stock exhaust manifold with no issues. I ran it that way (over a year) until just recently when I upgraded the manifold and cat to a 4-2-1 stainless header and high-flow cat.

One thing you may want to research is the manifold/cat you've pointed to in your post. I'm not sure about the '01-'05 cars, but on earlier Civics, the DX/LX models had a similar setup with the integrated cat. However, the EX models had a more traditional manifold/downpipe, with the cat further downstream as a separate unit. This means that the DX/LX cars can use the EX-style exhaust, which means your replacement options have increased dramatically.

Anyway, the point I'm getting to is that you may be able to buy a new manifold and cat separately, and do it for much, much cheaper than the price that's quoted. (On my '97, I ended up getting an EX-style header (stainless 4-2-1) and Magnaflow cat for around $220.)

Cool to know I can wait on the Header/Cat for awhile because of money of course lol.

Now with the whole buying an EX set up, I was told before, I had to do some custom modding of some sort and changing some sensors or something. I didn't want to have to go through any of that stuff. Just wanted to upgrade to a much better header/cat the easy way. IDK if those people were right or not so if you or anyone can help with that of course I'm open to hearing it because I've never messed with this stuff before until now.

I do know I can just simply get a bolt on header and a high performance cat for CHEAP but I found that COMBO I linked above with both and seemed better I guess. Thinking I might as well spend the money to get something I know will be good with my Exhaust system I'm getting.

speaking from experience i wouldn't bother getting a full headerback exhaust it just doesn't make enough gains on a D17 to justify the cost just get a nice axel back and call it a day. also aftermarket cats are no where near the quality of stock so if you have emissions test in your state don't plan on passing. that's a can of worms you don't want to open as for swapping to an EX system all you really need is the ex header and down pipe the only mod if you want to call it that is purchasing a oxygen sensor extension plug. like i said before just get a axel back and be done with it.

http://i22.photobucket.com/albums/b3...807_101903.jpg
Here is mine now, just the end piece I had welded on. It's not enough. I want the full effect with a cat back. The deep noise it will have and I don't want anymore air restrictions like how it is stock right now.

like i said before a full exhaust on these cars don't produce much of a gain. i currently have a AEM sri, megan 4-2-1 header to a full 2.5 inch exhaust no cat with a N1 style canister which netted me a whopping 5-8 hp not enough to even really feel. with that being said because of the small engine with no air restriction you actually lose low end torque gaining high end. as for the low growl sound your looking for has nothing to do with air restriction and everything to do with the muffler and most important the resonator. the resonator is what absorbs high pitch noise like the rasp you get with most cheap systems which most ricers have.

Damn, this is disappointing news. I don't want some ricer crap. I was just looking for my exhaust to be better and sound even better as in MEANER.

there are two setups ive heard that sound the best on EM2s the APEXI World Sport 2 catback or axelback and the Vibrant Street Power universal muffler with there Vibrant Ultra quite resonator. the general consensus is to stay away from canister style mufflers like the one you have for oval type mufflers for deeper sound. i actually prefer the vibrant setup which is also alot cheaper around $90 for the muffler another $90 for the resonator plus installation cost. if i was you id order the vibrant muffler have it installed then spend all that money you saved towards more important things like suspension or wheels.

Oh nice. Okay if I go with the Vibrant Street Power, I want the black look for my theme which is why I'm looking at their Flat Black Series.

So which Inlet/Outlet do I need for my stock piping for the best result? Vibrant Performance Mufflers ::.

Also what does the resonator do? Do I actually need one? And final question, if I get one which would I need because I see many sizes Vibrant Performance Resonator::.

Just for into, current Canister muffler I have now is
INLET: 2.5"
OUTLET: 4"
LENGTH: 12"

if yours is currently 2.5 then get the 2.5 inlet the outlet is not relevant. like i said before the resonator is like pre-muffler designed to absorb high pitch frequencies like the rasping you hear on ricer cars that sound like a swarm of angry bees. if you currently have the stock resonator you mite not even need the vibrant one since the stock resonator does a good job itself. have the muffler installed and see if you like it then go from there. if you get the vibrant resonator get the ultra quite one Vibrant Performance ::. its basically like your stock resonator .there's plenty of room under there pull out your tape measure and find out. also you can find them cheaper from online vendors just make sure there certified vendors CorSport: Vibrant - 1146